Phantomed signaling circuits



Oct. 30, 1923. 1,472,452

M. K. AKERS PHANTOMED S IGNALING- CIRCUITS Filed Sept. 5. 1920 //7 vanfor: /7/7f0/7 A. Akers Patented Oct. 30, 1923.

MILTON K. AKERS, OF EAST ORANGE. NEW JERSEY, ASSIGNOR TO WESTERNELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEWYORK.

PHANTOMED SIGNALING CIRCUITS.

Application'filed September 8, 1920. Serial No. 407,972.

To all whom it may concern:

Be it known that I, MILTON K. AKERs, a citizen of the United States,residing at 41 South lVa-lnut Street, East Orange, in the county ofEssex and State of New Jersey, have invented certain new and usefulImprovements in Phantomed Signaling Circuits, of which the following isa full, clear, concise, and exact description.

This invention relates to transmission systems and more particularly itrelates to signaling, lines, such as telephone lines, which are capableof being phantomed.

As is well known, in the art of telephony for example, an additionalsignaling circuit may be derived by phantoming two side circuits inwhich thesignaling currents for the third or phantom circuit pass in onedirection over the two wires in parallel of one side circuitand returnover the two wires in parallel of the other side circult. For ef-.ficient operation of such a derived phantomed circuit it is essentialthat the phantomed circuit currents be substantially equal in each ofthe two wires of each side circuit. Any inequality in the division ofthe phantomed currents will give rise to cross-talk, a result which ishighly undesirable. This inequality of the phantomed currents in the twoside circuit wires is due to some impedance irregularity in one or theother of the side wires and lines have frequently been encounteredhaving such irregularities that it has not been found feasible tophantom them.

In accordance with this invention it has been found possible to phantomside circuits with considerable impedance irregularities therein byderiving a current proportional to the amount of unbalance between thetwo wires of each side circuit and impressing this current on each wirein such a manner as to substantially equalize the currents in each pairof wires. Such a method of equalization of the phantomed currents isover a wide range substantially independent of the frequency.

This invention will be better understood by reference to the followingdetailed description taken in connection with the accompanying drawingwhich represents this invention as embodied in a telephone system.

The telephone system illustrated in the drawing comprises two sidecircuits composed of conductors 5, 6, and 7 8 respectively. Connected atone end of side circuits 5, 6 is a substation set A comprising atransmitter 10, receiver 11. transformer 12, and battery 13. Theopposite ends side circuit 5, 6 has a similar substation set Bcomprising a transmitter 14, receiver 15, transformer 16. and battery17. Side circuit 7, 8 is provided with similar substation sets C and D.

Shunted across the terminals of the two side circuits 5, 6, and 7. 8 arethe phantom coils 19, 20, 21 and 22 from intermediate points of whichconnections 24, 25, 26 and 27 are taken to the two substation sets E andF for the derived phantom circuit. The phantom circuit currents in sucha system may be considered for example, as passing over wires 5 and 6 inone direction and returning over wires 7 and 8 in the oppositedirection.

As is well-known in the art, such a phantom is feasible only when thereis a substantial equality in the phantom circuit currents in wires 5 and6 and in wires 7 and 8. Any inequality in a division of the phantomcircuit current between the two wires of each side circuit pair, givesrise to cross talk between the side circuit currents and the phantomcircuit currents, a result which is highly objection-able.

The manner in which side circuits may be phantomed, according to thisinvention, regardless of the tendency of one wire of each part tendingto carry more than its proportion of the phantom circuit currents, maybe explained as follows: Connected in shunt to the side circuit 5, 6 atthe end adjacent substation A is a transformer 35 having the threewindings 30, 31 and 32, which are preferably mounted on a single coilstructure. Inductively associated with the phantom coil 19 is aninductance element 33 which is in circuit with winding 31 of thetransformer 35. Windings 30 and 32 of transformer 35 are connected inseries with the phantom coil 19. A similar arrangement at that end ofside circuit 5, 6 adjacent substation B is shown comprising a transformer 36 having windings 37, 38 and 39; windings 37 and 39, of whichare in series with phantom coil 20, the other winding 38 is in circuitwith an inductance element 40 which is associated with the phantom coil20.

Suppose, for the purpose of illustration that line 5, due to impedanceirregularities tends to carry more than half of the phantom circuitcurrent. The phantom circuit current flowin r through connection 24 willtherefore ten to divide between the two halves of phantom coil 19 and inproportion to the length, for example, of the arrows shown adjacent coil19. Since that part of coil 19 in circuit with line 5 tends to carry themajority of the current, the current induced in winding 33 will be inthe direction of and proportional to the length of the arrow adjacentcoil 33. The current in coil 33 will flow through coil 31 and willproduce in windings 30 and 32 current components in the direction of thearrows adjacent these two windings. It will be observed that the currentinduced in coil 30 is in a direction opposite to the flow of the phantomcircuit current and will therefore tend to diminish the proportion ofthe phantom circuit current carried by wire 5. The current induced incoil 32, however, is in such a direction as to aid the phantom circuitcurrents in line 6 and therefore increase the amount of phantom circuitcurrent carried thereby. It follows therefore, that this arrangement ofthese inductive windin with respect to the phantom coil 19 Wlll. serveto substantially equalize the phantom circuit currents carried by wires5 and 6, regardless of differences in impedances of the two wires 5 and6. Such an arrangement, furthermore, is independent of the frequency,and therefore will produce a substantial equalization of the currentsover the whole telephonic range.

It is evident that the above described method cannot produce" anabsolutely perfect balance between the two wires 5 and 6 since such acondition would make the current in winding 33, zero and consequently nocurrent would be produced to create the corrective action necessary. Thearrangement however, reduces the cross talk between the phantom circuitand the side circuits.

The action of windings 37 and 40 inclusive which are associated withphantom coil 20 is similar to that described for the system associatedwith phantom coil 19.

In case the side circuit 7, 8, which is employed in connection with sidecircuit 5, 6 also tends to carry the phantom circuit currents in unequalproportions, arrangements similar to those described for phantom coils19 and 20 may be associated with the phantom coils 21 and 22. Thus inthedrawing, transformer 42 having windin s, 43, 44 and 45, is shown atthat end of side circuit 7, 8 adjacent substation C and a winding 46 isshown inductively related to phantom coil 21 and in circuit with winding44 of transformer 42. Similar inductive windings 49, 50, 51 and 52 areshown associated with the phantom coil 22 at that end of side circuit 7,8 adjacent substation D. However, if the side circuit associated withside circuit 5, 6 in order to produce a phantom circuit, is of such anature as to carry the phantom circuit currents equally without thenecessity of any correcting means, the phantom coils for the secondcircuit will not require the inductive windings associated therewith asshown in the drawing.

Although this invention has been described specifically in connectionwith a telephone system, it is to be understood that this invention isapplicable to other types of signaling systems such as telegraphsystems, composite systems, carrier current systems, and the like.

\Vhat is claimed is:

1. In combination, a line, a transformer having a winding in series withsaid line, a phantom tap connected to the midpoint of said winding, asecond transformer having a winding in circuit with a second winding ofthe first transformer, and having other windings connected in serieswith said line on opposite sides of said tap.

2. In combination, a two-wire line, a transformer winding in series withsaid line, a phantom circuit tap connected to the midpoint of saidwinding, a second winding inductively associated with said firstwinding, a third winding and a fourth winding connected in series withsaid first winding on opposite sides of said phantom tap, and a fifthwinding inductively associated with said third and said fourth windings,and connected in series with said 'second winding.

In witness whereof, I hereunto subscribe my name this 27th day ofAugust, A D. 1920.

MILTON K. AKERS.

